Understanding octane rating

A key factor for your engine

When you refuel, you’ve probably noticed different octane ratings available at the pump. Each has its advantages, adapted to specific situations. In this article, we will look at the most common octane numbers, namely 95, 98, 102, and E85, and discuss their appropriate uses.

What is Octane Rating?

The octane rating is a measure of fuel resistance to autoignition in the engine. More precisely, it indicates the fuel’s ability to resist knocking, an undesirable phenomenon that occurs when the air-fuel mixture ignites spontaneously before the ignition plug spark. Knocking can damage the engine if left unchecked, which is why the octane rating is so important.

Common Types of Octane Rating

Fuels are generally available with different octane ratings. The two most common are the RON (Research Octane Number) and the MON (Motor Octane Number). The RON is often the number you see displayed at the pump. The higher the number, the more resistant the fuel is to knocking.

95E10 - The forbidden fuel

95E10 fuel is one of the most common choices for everyday drivers. It contains up to 10% ethanol, which makes it less efficient than the 95 of yesteryear. 95E10 is a wise choice for everyday vehicles, but is totally prohibited for high-performance or reprogrammed vehicles.

98 - Multipurpose fuel

98 fuel, with a higher octane rating, is a versatile choice. It is recommended for high efficiency engines, sports vehicles and turbocharged engines. It also allows for optimal performance and better engine response. If you own a high-performance vehicle, choosing 98 fuel can improve overall performance.

102 - The best for your engine

102 fuel is specifically designed for high-performance vehicles and racing engines, making it WOT’s first choice. Based in Luxembourg, WOT refuels with 102 at Aral stations scattered across the country. Offering exceptionally high resistance to knocking, this recommended fuel is intended for motorsport enthusiasts who want to treat their engine as well as possible while enjoying optimal performance.

Note: Although 102 fuel is labelled E5 for legal reasons, it should be noted that it is distributed by Aral without the addition of ethanol, making it a fuel with a very high power capacity.

E85 - The ecological solution

E85 is a fuel that contains up to 85% ethanol. It is considered a more environmentally friendly option as it produces less greenhouse gas emissions. However, it is mainly suitable for flex-fuel vehicles, designed to work with ethanol blends. E85 offers a high octane rating, usually above 100, making it an interesting choice for racing enthusiasts who want to increase the power of their vehicle. This fuel is not as widespread as 102 octane and requires engine parameters to be modified and often a higher sizing of the injection system.

Why add ethanol to fuel?

In order to reduce dependence on crude oil and reduce CO2 emissions, Europe took the decision over ten years ago to introduce ethanol to unleaded petrol. However, despite its advantages, this initiative only has positive effects on the performance of modern vehicles. Indeed, as previously mentioned, pure ethanol improves the octane rating, therefore a lower quality fuel is mixed with ethanol to reach octane levels of 95 to 98. This combination leads to decreased power performance and a change in knocking noise. As a result, engine sensors sometimes struggle to detect autoignition correctly, which leads to an additional risk. Therefore, it is recommended to choose a fuel containing as little ethanol as possible, i.e., 5% (for example: 98E5).

In summary, the choice of octane rating is crucial, both for the performance of your vehicle and for the reliability of its engine. It is best, insofar as possible, to avoid the use of 95E10 fuel, which yields poor performance and relatively inferior quality. For daily use, WOT recommends choosing a fuel with an octane rating of 98, containing as little ethanol as possible, i.e., 5% (98E5). If a petrol station selling 102 fuel is handy, we strongly encourage you to give preference to this fuel, guaranteeing best performance and yields. Finally, we strongly advise against mixing different types of fuel as this could lead to decreased performance of your vehicle.